1. Field of the Invention
The present invention relates to a transverse beam as an at least indirect component of a composite suspension control arm shaft. The present invention also relates to a method of manufacturing such a transverse beam.
2. Description of the Related Art
EP 0 229 576 B1 discloses a composite control arm shaft manufactured from a pipe, wherein the longitudinal control arms of the control arm shaft extend parallel to each other and are tubular without being deformed. Except for its also circular tubular ends, the transverse beam, which connects the longitudinal control arms in a manner which is stiff with respect to bending but yielding with respect to torsion, has a cross-section which is L-shaped, V-shaped, T-shaped, U-shaped, X-shaped or H-shaped.
In the past, a composite control arm shaft of this type could not be used in actual practice because of problems with respect to the required service life. The reason that a satisfactory service life could not be achieved is in U-shaped and V-shaped transverse beams the high load occurring in the transition areas between the deformed length portion and the non-deformed length portion, so that premature failure occurs in these areas in the case of a continuous use.
In contrast, transverse beams deformed into an X-shape or a Y-shape have a longer service life because the shearing center coincides with the center of gravity of the transverse beam. However, these cross-sections have the disadvantage of a limited possibility of varying the bending stiffness in relation to the weight and the positioning of the shearing center of the transverse beam which is responsible for the running characteristics.
DE 27 35 939 B1 discloses a composite axial system for motor vehicles in which two tubular longitudinal control arms are connected to each other in an angle-stiff manner by a V-shaped transverse rod. The transverse rod is composed of a single layer and has a V-shaped, cross-section over the entire length. In the transition areas from the transverse rod to the longitudinal control arms, separately manufactured, shoe-shaped gusset plates are welded to the transverse rod and to the longitudinal control arms. The transverse rod has embossed corrugations in its apex area in front of the end faces of the gusset plates facing the vertical transverse middle plane of the transverse beam.
In order to construct the transition areas between the deformed length portions and the non-deformed length portions which are subjected to the highest loads in such a way that the occurring stresses are uniformly distributed over the entire section area, European patent application 0 752 332 discloses a transverse control arm which has circular tubular end portions and a torsion portion in the middle formed by chipless deformation of a double-wall U-shaped section, wherein the intermediate portions between the end portions and the torsion portion change continuously from the circular cross-section to the U-shaped cross-section, and wherein the transverse control arm is at the ends of the U-shaped portion and at the arc-shaped web provided with inwardly and outwardly directed embossments with rounded edges.